He was a Progressive Conservative member of the Legislative Assembly of Ontario from 1995 to 1999 and a prominent cabinet minister in the government of Mike Harris.
Before he entered politics, Leach spent 23 years in various managerial positions with the Ministry of Transportation of the Government of Ontario.
He was hired as Chief General Manager of the Toronto Transit Commission in 1987 and served in that position until he resigned in early 1995 to seek political office.
Leach was appointed as the Harris government's Minister of Municipal Affairs and Housing on June 26, 1995, and held this position until the 1999 provincial election.
[2] In that capacity, Leach presided over a number of controversial issues, including amalgamating the City of Toronto with five of its suburbs, ending rent control, and cutting provincial grants to the metropolitan region.
In 2000 Leach joined the firm of SNC-Lavalin, Canada's largest engineering and construction company and was a member of the board of directors.